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Add a raw mapped LUN to a VM in VMware ESXi

You have a LUN that needs to be added via raw mapping to a VM in ESXi. This is often done to access a LUN on a SAN or iSCSI NAS that is already formatted as Windows NTFS, Linux ext3, etc. It’s a type of “pass-through” LUN that you would map to VMware and then into a VM.

BE CAREFUL! Many filesystems, e.g., NTFS, can only be used by one computer at a time! If you open an NTFS volume on two Windows computers at once you will most likely permanently destroy that NTFS volume!


You can do this in vSphere Client.

  1. In vSphere Client, choose the VM to add the RAW LUN mapping and click Edit virtual machine settings
  2. On the Virtual Machine Properties page Hardware tab, click Add… Under Device Type, choose Hard Disk and click Next
  3. Click the Raw Device Mappings option and click Next (If this option is greyed out, see the note at the end of this post)
  4. Choose the LUN you wish to map and click Next
  5. Choose where the RDM will be stored, with the Virtual Machine is default. Click Next
  6. Choose the compatibility mode for the disk and click Next
  7. Choose the controller type and node, then click Next
  8. Click Finish
  9. Back at the Properties page, click OK
  10. Wait for the task to complete successfully
  11. Log in and verify your HDD is usable


  • For Dell MD32xx SAS Storage Arrays, the RdmFilter.HbaShared checkbox must be deselected on your ESXi host:
    • In vSphere Client, select your host, click the Configuration tab, then click Advanced Settings under Software
    • Scroll down to RdmFilter, deselect the check box, click OK
  • For other potential causes and resolutions for a grayed out RDM option, please refer to VMWare KB 1017704:
    • http://kb.vmware.com/selfservice/microsites/search.do?language=en_US&cmd=displayKC&externalId=1017704

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